Problem is your code is hard to follow: there is a loop which body is ove 90 lines. All variables declared in the beginning with no regard of their actual scope.
Ideally your main function should look like:

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int main()
{
bool use_again;
do {
quadraticEquation();
use_again = askQuestion("Would you like to use this program again?");
} while ( use_again );
return 0;
}